The correct answer is - b. combining a single oxygen atom (O) with an oxygen molecule (O2).
The ''good ozone'' in the stratosphere, is formed by the combination of a single oxygen atom with an oxygen molecule of two oxygen atoms. This ozone is actually forming a layer, something like a subdivision in the stratosphere, where it is dominant, and it is of huge importance for the life on the Earth.
The ozone layer is managing to control the amount of ultraviolet light that come towards the Earth from the Sun, and if the ozone layer doesn't do that, than the life on our planet will be very hard, as the ultraviolet light is extremely damaging for the living organisms.
